How do these class mesh with regular classes?

[WarlockDa]

We're currently running Rise of the Runelords, and I'm debating on allowing the players to test an advanced class or two, but worried if that would create any issues. Looking over the guide I haven't seen anything glaring.

Anyone have any experience to share? Our group games very infrequently so I don't want to run a full blown testing session and miss out on progress in our campaign.

Thanks in advance!

[Cap. Darling]

I think a gunslinger will give you more problems than any of the hybrids.